A solid-state imaging device in which a charge accumulation portion is provided between each pixel portion and an offset gate portion to switch resolution is known as a related art solid-state imaging device.
In this solid-state imaging device, a charge accumulation portion is a region which temporarily accumulates a charge produced in each pixel portion, and has an N-type charge accumulation layer provided on a surface of a P-type well layer on a surface of a semiconductor substrate. The charge accumulation layer is provided by injecting impurities in a wide range of the surface of the well layer.
However, when a charge accumulation layer has a wide area as described above, a deepest portion of an electric potential of a charge accumulation portion is provided near the center of the charge accumulation portion. Although a charge accumulated in the charge accumulation portion is transferred to an offset gate portion by applying a voltage to a transfer gate portion between the charge accumulation portion and the offset gate portion, when a deepest portion of an electric potential is formed near the center of the charge accumulation portion, the charge is likely to be accumulated near the center of the charge accumulation portion. Thus, the charge is accumulated at a site distant from the transfer gate portion, and therefore the voltage to be applied to the transfer gate portion to transfer the charge increases. As a result, there is a problem that a voltage margin of the voltage to be applied to the transfer gate portion is small, and it is difficult to read the charge at a low voltage.